The present invention relates to a boat steering arrangement comprising a main steering system and a control-surface assembly attached to the stern of a boat (that is, any water-borne vessel). Control surfaces of a boat include rudders, hydroplanes and other hinged or movable devices, such as trim tabs, used for controlling the motion of the boat.
As is well known, adjustable trim tabs positioned at the stern of a boat are often used to get the boat to the plane mode as quickly as possible; the boat is then maintained at its most economical cruising speed by tab adjustment. Relative adjustment of port and starboard trim tabs also enables the elimination or reduction of listing or heeling.
More generally, control surfaces may be taken to include static elements such as fixed vertical fins which assist in boat control by, for example, minimizing unwanted lateral movement. Thus, as a means to improve directional stability for watercraft, it is common practice to use fixed underwater fins or ‘skegs’ at a point as near as possible to the back of the vessel. In general, skegs reduce “side slip” of the vessel when in forward motion. Shallow draft vessels are more prone to side slip than vessels of deeper draft design.
As used herein, the term “skeg” means a fixed or movable vertical control surface; typically, but without limitation, a skeg takes the form of a small vertical fin; in this context, the term “vertical” is used herein to include any inclination that is nearer the true vertical than the true horizontal.
In various situations, it is desirable to provide a boat with movable control surfaces for steering additional to the main steering surfaces. For example, certain types of boat, such as jet drive boats, while being highly manoeuvrable at speed, are difficult to steer at low speed. Also, boats that operate offshore may be required to possess an emergency steering system that is independent of the main steering system.
One way of providing additional steering functionality is to install auxiliary movable vertical control surfaces. However, such control surfaces are potentially vulnerable to damage, particularly where the boat concerned is intended for shallow water operation or for launch and recovery to/from a road trailer.